The main objective of this proposal is to genetically and biochemically characterize baculoviruses which are currently produced as biological insecticides and are widely distributed in the environment. A series of temperature-sensitive (ts) mutants of the Autographa californica nuclear polyhedrosis virus (AcMNPV) will be isolated. The mutants will be grouped by complementation analysis and characterized by their ability to produce extracellular nonoccluded virus and/or occluded virus. Categorization of the mutants into early and late classes will be determined by monitoring DNA synthesis. A series of deletion mutants defective in occlusion will be generated in vitro by partial restriction endonuclease digestion followed by transfection of cell cultures. The biochemical analysis of baculovirus infections will be directed at determining the types of virus-induced enzymes. Enzymes to be screened include DNA polymerases, RNA polymerases, nucleases, and kinases. The studies will provide further information relevant to the safety of spraying these viruses as biological insecticides.